Wireless & Mobile Networks By Dr. Ali Maqousi amaqousi@uop. edu. jo Feb, 2012
Introduction n n History: - In 1831 Joseph Henry, sends an electric current over a wire to activate an electromagnet, which caused a bell to ring. In 1844 Samuel Morse, invented the telegraph. In 1876 Alexander Graham, laid the foundation of telephone by making the first voice call over a wire. Marconi invented the wireless telegraph in 1896 n Communication by encoding alphanumeric characters in analog signal, Sent telegraphic signals across the Atlantic Ocean In 1957 USSR (now Russia) launched the first artificial earth satellite (Sputnik). 2
Introduction n Wireless-First step: - In 1947 AT&T Bell Labs researchers realized that by using small service areas or cells they can reuse the frequency. So the hexagonal cells for mobile phones were invented. However due to the limited number of channels (the license), which supports only 23 customers at a time, the implementation was stopped. Did not support the automatic change of channel frequency in the middle of a call, when the user moved from one cell to another (handover) feature (0 G). 3
Introduction n n Evolution of wireless Technology: First Generation (1 G) uses the analog technology. It uses FDMA (Frequency Division Multiple Access) technology for modulation. The second generation (2 G) technology uses digitized technology. It uses a combination of TDMA (Time Division Multiple Access) and FDMA technologies, e. g. GSM. In 2 G technology voice is digitized over a circuit. In 1 G and 2 G networks the case is similar to what happen in a dial-up network over analog telephones at home. 4
Introduction n n Evolution of wireless Technology: (Cont…) In 2. 5 G technology, voice is digitized over a circuit, however, data is packetized. 2. 5 G uses the same encoding techniques as 2 G does. E. g. of 2. 5 G is GPRS networks. 3 G wireless technology uses spread spectrum techniques for media access and encoding. In 3 G networks both voice and data use packets. E. g. are UMTS and CDMA 2000. 4 G technology makes information transfer and internet capabilities faster and more affordable for cellular phones. Researchers are still motivated to make advances in 4 G. E. g. Long Term Evolution (LTE) technology. 5
Wireless Applications • Wireless applications are found anywhere employees need mobility, including in the following industries: – Education – Military – Business – Entertainment – Travel – Construction – Warehouse management – Health care 6
Advantages of Wireless & Mobile Networks • • No need to install and maintain wires Reduces cost –important in offices, hotels, … Simplifies deployment –important in homes, hotspots, … Supports mobile users: – – Move around office, campus, city, … -users get hooked Remote control devices (TV, garage door, . . ) Cordless phones, cell phones, . . Wi. Fi, GPRS, Wi. Max, … 7
Disadvantages of Wireless & Mobile Networks • • Quality of transmission Interference and noise Capacity of the network Effects of mobility 8
Wireless & Mobile Networks Space 9
Limitations and Difficulties of Wireless Technologies n Limitations and political and technical difficulties inhibit wireless technologies: 1 - Lack of an industry-wide standard. 2 - Device limitations n E. g. , small LCD on a mobile telephone can only displaying a few lines of text n E. g. , browsers of most mobile wireless devices use wireless markup language (WML) instead of HTML 10
Limitations and Difficulties of Wireless Technologies (Cont. . ) • • Power consumption – limited computing power, due to limited battery capacity Loss of data – higher probability of loss of data, has to be included in advance into the design. Limited user interfaces – compromise between size of fingers and portability – integration of character/voice recognition, abstract symbols Limited memory 11
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